The growth of networks capable of handling high data-rate transfer of voice and data has created a demand for optical networks. While information can be transferred optically over large distances, there is also a need for interfacing the optical portion of an optical network with electrical and electro-optical components. Thus, for example, optical networks include amplifiers for strengthening optical beams, switches for routing signals, and conversions between electrical and optical signals at either end of the network. These functions are performed by devices that include optical, electro-optical and electrical components.
As with electronic devices, it is advantageous to arrange optical and electro-optical components in a chip-like configuration on a circuit board that allows for interconnection between devices. Numerous methods have been proposed for the interconnection of optical beams of integrated circuit chips. Each of these methods has problems in aligning or having losses in the transmission of the optical beam, or is expensive or difficult to produce or use. Other problems occur when attempting to scale the proposed methods to accommodate a large number of optical beams.
In one system, an electro-optical chip is positioned over a substrate with a ball grid array. An emitter of the chip is aligned with a waveguide on the substrate, and signals are transmitted between the chip and substrate without an intervening material, that is, the interconnection is through free space. Since there is nothing to guide the beam between the components, such a system is susceptible to losses mostly due to component misalignment and the light beam divergence. Lenses can be used to couple the beam between the transmitter and the waveguide as well as between the waveguide and receiver. However, the lenses need to be well aligned with the other components and also have back reflections that results in additional optical power losses. In another system, optoelectronic transmitters and receivers are coupled without wave guiding structures. The emitted light is collimated in beams of 0.5–1 mm size and the holographic optical elements (“HOEs”) or other coupling gratings are used to direct optical beams from optoelectronic transmitters directly into receivers located at a relatively large distance, usually more than 10 mm. This type of interconnect has the disadvantage of very difficult alignment procedures as well as of space required for the collimating lenses and thus reduced possibilities for compact integration.
Therefore, it would be desirable to have an optical interconnect and method that are compatible with existing interconnect technology, are relatively insensitive to slight misalignment between the components, have minimal or no optical loss, that prevent particles from interfering with light transmission, and that can be easily scaled to devices that transmit many optical beams. It is also desirable to have an optical connection and method that does not require extensive processing of the chips and that is reliable and relatively inexpensive.